Low-dose recombinant canine interferon-gamma for treatment of canine atopic dermatitis: an open randomized comparative trial of two doses.

The purpose of this study was to investigate the minimum effective dose of recombinant canine interferon-gamma (rCaIFN-gamma) for the treatment of dogs with atopic dermatitis (AD). Thirty-four dogs with AD from 17 animal hospitals in Japan were administered half or one-fifth of the approved rCaIFN-gamma dose of 10 000 units/kg, three times a week for 4 weeks, followed by once weekly for an additional 4 weeks. Pruritus, excoriation, erythema and alopecia were evaluated and scored by the investigators on weeks 2, 4, 6, 8 and 12. The efficacy rate (number of excellent cases + number of good cases/total number of cases) at week 8 in the 2000 units/kg group was 36.4% for pruritus, 36.4% for excoriation, 45.5% for erythema and 36.4% for alopecia. In contrast, in the 5000 units/kg group, the efficacy rate was 64.3% for pruritus, 57.1% for excoriation, 78.6% for erythema and 78.6% for alopecia. The efficacy rate of the 5000 units/kg group was high for all signs evaluated and comparable to that of the 10 000 units/kg group reported in a previous study. The results of this study showed that 2000 units/kg of rCaIFN-gamma is less effective than 5000 units/kg to treat dogs with AD, and the efficacy of the 5000 units/kg dose is comparable to that of 10 000 units/kg at week 8.

Measurement of feline serum interleukin-5 level.

A bioassay was developed to measure feline interleukin-5 (IL-5). Human IL-5 receptor alpha chain transfected murine Ba/F3 cells (Ba/F3-IL-5R) showed feline IL-5-dependent proliferation in a dose-dependent manner. IL-5 levels in serum samples from 54 cats with suspected allergic dermatitis and from 11 control cats could be successfully measured using Ba/F3-IL-5R cells. The number of eosinophils in peripheral blood was not correlated with serum IL-5 level.

Plasma histamine concentration and histamine detection in peripheral blood eosinophils in cats.

Plasma histamine levels were measured in 11 clinically healthy cats and 15 cats with allergic dermatitis. Histamine levels were markedly elevated in 5/15 allergic cats. A calcium ionophore, A23187, stimulates histamine release from feline peripheral blood cells. Immunostaining of blood smears from clinically healthy cats revealed that approximately 10% of eosinophils possessed histamine-containing granules. These results indicate that some peripheral eosinophils in cats contain histamine and can release histamine by appropriate stimulation.

Allergen-specific immunotherapy induces Th1 shift in dogs with atopic dermatitis.

Allergen-specific immunotherapy has been applied to canine atopic dermatitis. Despite the accumulated clinical evidence of its effect for atopic dogs, the basic immunologic mechanisms were not fully understood. In this study, the cytokine profile ex vivo in canine atopic dermatitis before and after allergen-specific immunotherapy was characterized using competitive reverse transcription-polymerase chain reaction (RT-PCR). Blood samples were collected from 10 dogs with atopic dermatitis and peripheral blood mononuclear cells were stimulated with house dust mite antigen. The levels of IFN-gamma and IL-4 mRNA were lower in atopic dogs compared with non-atopic controls. The ratio of IFN-gamma/IL-4 was low in atopic dogs indicating a cytokine profile polarized to Th2. The level of IFN-gamma after immunotherapy was significantly higher than that before (P < 0.05) whereas that of IL-4 mRNA was not changed. Consequently, the ratio of IFN-gamma/IL-4 after immunotherapy was significantly higher than that before immunotherapy (P < 0.05). These results indicate a Th2 cytokine bias is the dominant state in atopic dogs and allergen-specific immunotherapy causes a shift to wards a Th1 bias by enhancing IFN-gamma expression.